The article examines the interdependent key terms “transport security” and “act of unlawful interference” used in the legal mechanism of administrative and legal regulation of public relations in the field of transport security. The subject analysis is based on the interpretation of their understanding in Russian law, on the study of the genesis of scientific thought on the formation of these terms before the adoption of the Federal Law “On Transport Safety” and in modern realities. Clarifications of legally established definitions aimed at distinguishing transport security from other types of transport security by types of threats, objects of protection and means of its provision are proposed.